Organization, Basis of Presentation and Significant Accounting Policies (Details 2) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Basic and diluted shares outstanding
Weighted average common shares - basic (in shares)	139,340,142			137,848,788			138,931,955	137,818,076
Weighted average DownREIT units outstanding (in shares)	7,500			7,500			7,500	7,500
Effect of dilutive securities (in shares)	505,032			466,776			498,609	405,148
Weighted average common shares - diluted (in shares)	139,852,674			138,323,064			139,438,064	138,230,724
Calculation of Earnings per Share - basic
Net income attributable to common stockholders	$ 279,677	$ 168,281	$ 170,366	$ 192,486	$ 254,662	$ 141,643	$ 618,324	$ 588,791
Net income allocated to unvested restricted shares	(704)			(555)			(1,655)	(1,722)
Net income attributable to common stockholders, adjusted	$ 278,973			$ 191,931			$ 616,669	$ 587,069
Weighted average common shares - basic (in shares)	139,340,142			137,848,788			138,931,955	137,818,076
Earnings per common share - basic (in dollars per share)	$ 2.00			$ 1.39			$ 4.44	$ 4.26
Calculation of Earnings per Share - diluted
Net income attributable to common stockholders	$ 279,677	$ 168,281	$ 170,366	$ 192,486	$ 254,662	$ 141,643	$ 618,324	$ 588,791
Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships	11			11			34	33
Adjusted net income attributable to common stockholders	$ 279,688			$ 192,497			$ 618,358	$ 588,824
Weighted average common shares - diluted (in shares)	139,852,674			138,323,064			139,438,064	138,230,724
Earnings per common share - diluted (in dollars per share)	$ 2.00			$ 1.39			$ 4.43	$ 4.26